This invention relates to a method of producing polycarbonate by a catalyzed interfacial polycondensation polycarbonate process wherein the polycarbonate is formed in the aqueous phase by using a low organic to aqueous phase volume ratio. More particularly, this invention involves the addition of ionic surfactants to the aqueous phase of the reaction medium to provide more useful polycarbonates.
An interfacial polycondensation polycarbonate process wherein the polycarbonate is formed in the liquid aqueous phase has been reported by Sikdar in U.S. Pat. No. 4,368,315, assigned to the same assignee as the present invention. Sikdar discloses the use of a two-phase reactant admixture containing a liquid inert organic solvent phase and a liquid aqueous phase having a volume ratio within the range of from 0.04:1 to 0.20:1 during the preparation of an aromatic polycarbonate having a weight-average molecular weight (M.sub.W) of at least about 2000. The process disclosed by Sikdar provides the benefits of (1) utilizing reduced amounts of liquid phase inert organic solvent during the poly-condensation process and (2) the elimination or reduced use of (a) an antisolvent in the separation and recovery of polycarbonate from the reaction environment and/or (b) steam precipitation to recover polycarbonate from the organic phase. This is permitted since substantially all the polycarbonate formed precipitates in-situ in the aqueous phase.
While this process has provided acceptable aromatic polycarbonates, there still remains room for improvement. For example, the process comprising this invention produces more useful polycarbonates having intrinsic viscosities above 0.4 dl/g. The most useful polycarbonates generally have intrinsic viscosities within the range of 0.4 to 0.7 dl/g. In addition, where a phase ratio above 0.08 is utilized in the process disclosed by Sikdar, the polycarbonate often precipitates as agglomerated solids rather than fine particles. This invention overcomes the problem of agglomeration and produces polycarbonate in particulate form over a wider range of process variables.